The present invention relates to a motor-driven compressor that includes an inverter assembly.
Generally, a motor-driven compressor includes a compression mechanism compressing refrigerant gas, an electric motor driving the compression mechanism and an inverter assembly controlling the rotation of the electric motor. The inverter assembly has therein a circuit board on which electronic parts forming an inverter circuit are mounted.
During the operation of the motor-driven compressor, the electronic parts mounted on the circuit board of the inverter assembly generate heat and the operation of the compression mechanism causes the circuit board to be vibrated. For protecting the electronic parts on the circuit board from such heat and vibration, the inverter assembly is disposed on the outer surface of a compressor housing that is adjacent to a passage through which low-temperature and low-pressure refrigerant gas just introduced into the compressor housing flows and, additionally, thermally conductive and elastic resin is provided in the inverter assembly. In operation of the motor-driven compressor, the heat generated by the electronic parts is transferred through the resin to the housing and released therefrom. The vibration caused by the compression mechanism is absorbed by the resin.
Japanese Patent Application Publication 2004-251161 discloses a motor-driven compressor whose inverter assembly is mounted on the outer surface of the compressor housing adjacent to a passage of low-temperature and low-pressure refrigerant gas. Furthermore, a support member made of resin is interposed between the closed end of the inverter assembly and a circuit board in the inverter assembly and additionally a thermally conductive and elastic rubber sheet is interposed between electric parts mounted on the circuit board and the outer surface of the compressor housing. During the operation of the motor-driven compressor, the heat generated by the electric parts is transferred through the thermally conductive and elastic rubber sheet to the outer surface of the compressor housing and released therefrom and the vibration caused by the compression mechanism is absorbed by the thermally conductive and elastic rubber sheet.
In a conventional case where resin is provided in the entire interior of the inverter assembly of the compressor, a large amount of resin need be used and an air hole be formed through housing of the inverter assembly for preventing pressure change in the inverter assembly occurring due to temperature increase, with the result that material and the manufacturing costs of the inverter assembly increase. In the case of the inverter assembly of the motor-driven compressor according to the above Publication which uses the support member made of resin and the thermally conductive and elastic rubber sheet, the heat generated by the electronic parts can be released to the compressor housing through the rubber sheet, but the heat transferred from the electronic parts to the circuit board can not be released to the compressor housing, so that high radiation efficiency can not be achieved.
The present invention is directed to providing a motor-driven compressor with an inverter assembly that is less costly than heretofore and offers high radiation performance and vibration resistance.